The present invention relates to a telecommunications apparatus, and more particularly, to a telecommunications apparatus of a type typically used in telecommunications stations and having reduced electromagnetic interference (EMI) radiation, improved flame resistance and improved ease of expansion.
Together with the growing importance of telecommunications in recent years there is a growing need for improvements in the quality of the telecommunications equipment used in exchanges and the like. One such improvement in quality has to do with lowering the amount of EMI radiated from such equipment, done for example by meeting the FCC standards embodied in Part 18 of the FCC regulations and adopted in North America, and additionally, by having flame resistance such that a fire does not spread if for example one breaks out within the telecommunications equipment.
Additionally, though not directly related to essential performance of the telecommunications equipment, users do value an ability to accommodate changes in future telecommunications operations, such as an increase in telecommunication lines, that is, ease of expansion.
Generally, such telecommunications equipment consists of a plurality of plug-in units aligned within a sub-rack which is mounted in a rack.
A cover provided on the front of the sub-rack into which the plug-in units are inserted in order to reduce EMI emissions is the EMI countermeasure conventionally adopted. This construction is designed to shield the electromagnetic interference radiated from the loaded plug-in unit. However, with this construction, there was a danger that the EMI countermeasures would be insufficient.
As for flame resistance, conventionally the approach taken has been a metallic plate member provided opposite a printed circuit board of the plug-in unit. In this composition, a peripheral portion of the printed circuit board was exposed directly to the flame, so there was a danger that the fire would spread and thus flame resistance was insufficient.
With respect to ease of expansion, consider a case in which a loaded plug-in unit of normal height is removed and in its place two plug-in units of half the normal height are loaded. Conventionally, vertical as well as horizontal partitions are mounted inside the sub-rack, partitioning a portion of the interior of the sub-rack in two, and then plug-in units of half the normal height are inserted, expanding capacity. The vertical partitions have the function of supporting the horizontal partitions at one edge. In this construction, the operation of mounting the partitions is troublesome, and further, it is difficult to precisely position the partitions so as to form a space in which a single plug-in unit is contained, and so it was not easy to perform an expansion.
The present invention has as its overall object to provide a telecommunications apparatus that solves the above-described problems of the conventional art.
A more specific object of the present invention is to provide a telecommunications apparatus that satisfactorily lowers electromagnetic interference radiated to the outside from the telecommunications apparatus and that has fire resistance such that a fire does not spread even if one breaks out inside the telecommunications apparatus.
In order to achieve these objects, the present invention provides a telecommunications apparatus comprising a box-like sub-rack unit having a back wiring board and a guide rail portion and a plurality of plug-in units inserted and loaded into the sub-rack unit from a front surface thereof along the guide rail portion,
the sub-rack unit configured so as to have a back wiring board frame plate having ribs provided on a front of the back wiring board,
the plug-in unit comprising:
a metallic front member;
a printed board fixedly mounted at one edge on the front member and having, at a leading edge in a direction of insertion, a connector designed to be connected to the back wiring board when loaded; and
a metallic case that envelopes the printed board and has an opening on a leading edge in a direction of insertion that exposes the connector,
the plug-in unit configured so that an entire peripheral edge of the opening on the leading edge in the direction of insertion of the metal case contacts the back wiring board frame plate ribs in a state in which the plug-in unit is mounted in the sub-rack unit.
According to this type of telecommunications apparatus, by having the metallic case cover and envelope the printed board, the radiation of electromagnetic interference outward from the mounted individual plug-in units can be limited. Accordingly, it is possible to satisfactorily lower the electromagnetic. interference radiated to the outside from the telecommunications apparatus. Additionally, by having the metallic case cover and envelope the printed board, flames from a fire can be checked from reaching the printed board so that the fire does not spread.
Another object of the present invention is to provide a telecommunications apparatus designed for ease of expansion.
In order to achieve these objects, the present invention provides a sub-rack unit comprising:
a lock nut member mounted so as to straddle rear surfaces of adjacent ribs on the back wiring board frame plate and having a lock nut that projects proximally; and
an intermediate guide rail member having guide rails on upper and lower surfaces with a lock bolt member retained inside and an opening in which a tool is inserted so as to rotate the lock bolt member,
the intermediate guide rail member being inserted into the sub-rack unit from a front surface thereof and mounted by similarly threading the lock bolt member into the lock nut of the lock nut member from the sub-rack unit front surface.
The operation of mounting the intermediate guide rail is possible entirely from the front of the sub-rack unit. Accordingly, the operation of mounting the intermediate guide rail member is easy, and expansion can also be done easily.
These and other objects, features and advantages of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.